The present invention relates to electrical extension and power supply cords and, more particularly, relates to electrical extension and power supply cords which include built-in safety protection.
The ubiquitous extension cord, found in practically every residence wired with electrical power, needs little introduction. A complete extension cord includes a plug, usually comprising two or three prongs, a cord, typically comprising two or three insulated wires several feet in length and a terminal connector or receptacle for receiving one or more electrical plugs to power lamps, radios, televisions, household appliances, etc. A grounded extension cord includes a plug having three prongs and a three insulated wire cord, two wires of which are utilized for phase and return power and a third utilized as common ground. While extension cord use presents many advantages, there are some disadvantages associated as well. For example, extension cords are often left underneath rugs where they are trampled and pinched by doors and furniture, leading to arcing or short circuiting, which can cause fire. Extension cords also frequently tend to be left coiled whereby heat can concentrate, or are overloaded to the point of destruction by fire. Given the number of dangerous situations which could develop pursuant to extension cord use and abuse, such as residential fires and electrocution, an extension cord design offering some protection in anticipation of homeowner/user abuse would be well received.
An electrical extension cord including safety protection would be particularly well received at premises occupied by inquisitive young children. To say the least, such a population is known to probe and/or taste every "thing" they come into contract with. In particular, electrical extension cord receptacles may very well include unused ports into which conductive foreign objects such as paper clips, keys, screwdrivers, and the like may be inserted by an exploring child. This activity may very well result in electrical shock, which could injure or, in the worst case, kill the child. The danger has long been recognized and extension cord manufacturers have made various attempts to prevent such injuries.
For example, one prior art approach for improving the safety of electrical extension cords uses a pseudo twin-prong plug formed of a non-conductive material to block access to unused receptacle ports. Unfortunately, however, children appear to have no more difficulty than adults in removing such plugs from the receptacles in which they reside. Another conventional approach includes the use of a disk rotatably mounted to cover the receptacle ports, such as an arrangement described in U.S. Pat. No. 4,879,098. Yet another approach includes the use of moveable plates to prevent access to electrical receptacle ports. For example, U.S. Pat. No. 4,810,070 discloses the use of a plate held to the connector body by flanges, and U.S. Pat. No. 4,094,569 discloses the use of a plate secured to the connector body by a central barbed stake. Access to each receptacle port requires using the plug for insertion as a tool to align port slots and thereby enable insertion of the plug. While such remedies may offer some support in efforts to prevent misuse of plugs or receptacles associated with electrical extension cords, such remedies do not address problems associated with trampled, pinched, ruptured or overloaded electrical power and/or extension cords.